During the past decades there have been considerable developments within the fields of radiation therapy and medical diagnosis. The performance of external beam radiation therapy accelerators, brachytherapy and other specialized radiation therapy equipment has improved rapidly. Developments taking place in the quality and adaptability of radiation beams have included new targets and filters, improved accelerators, increased flexibility in beam-shaping through new applicators, collimator and scanning systems and beam compensation techniques, and improved dosimetric and geometric treatment verification methods have been introduced.
Furthermore, a number of powerful 3-dimensional diagnostic techniques have been developed, ranging from computed tomography (CT), positron and single photon emission computed tomography (PET and SPECT) to ultrasound and magnetic resonance imaging and spectroscopy (MRI and MRS). Equally important is the increased knowledge of the biological effect of fractionated uniform and non-uniform dose delivery to tumors and normal tissues and new assay techniques, including the determination of effective cell doubling times and individual tissue sensitivities, allowing optimization of the dose delivery to tumors of complex shape and advanced stages.
A major problem in the field of radiation therapy and diagnosis today is the accurate positioning of a patient on a patient couch prior radiation therapy or diagnosis in order to achieve correct position of patient body parts to be treated or diagnosed.
US 2005/0283068 discloses a motion tracker for a MRI system. A structure comprising infrared (IR) reflectors is mechanically attached to the patient body. An IR scanner projects IR light onto the IR reflectors and a camera is arranged for monitoring the motion of the IR reflectors in real time. Feedback information in up to six dimensions can be obtained both before and during MRI scanning. The feedback information is displayed on a display screen for the patient or medical personnel trying to reposition the patient based on the feedback information.
A disadvantage of the system of US 2005/0283068 and similar patient positioning systems of the prior art is that the feedback information defining how the patient body should be repositioned is displayed on a display screen. This display screen generally has to be arranged a distance away from the radiation system to allow the gantry sufficient space to rotate safely around the patient without any risk of hitting the display screen. However, such a remote arrangement of the display screen in relation to the couch onto which the patient is lying makes it cumbersome for the medical personnel standing next to the couch and patient to correctly reposition the patient while simultaneously looking at the remote display screen.